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sites of many ancient cities were determined, were eventually published by Messrs. Spratt and Forbes; but these 'Lycian Travels,' however interesting, must be considered as of very secondary importance, so far as Edward Forbes is concerned, to the results of his examination of the shores of the Ægean with the dredge, an instrument of great simplicity indeed, but with whose value he had early acquainted himself. It was upon the data obtained by dredging during his cruises that he based that remarkable 'Theory of the Bathymetrical Distribution of Life' with which his name will always stand most prominently connected in the annals of science.
That zones of distinct species of living beings may be shown to exist at different depths in the sea—just as corresponding zones are demonstrable at different heights on the land,—is a proposition which had been clearly enunciated by Audouin and Milne-Edwards so long ago as 1832, and subsequently, on independent grounds, by Loven. But, for the addition of new zones, for their accurate enumeration and definition, and above all, for the practical application of the 'Theory of Distribution in Depth, of Marine Life,' to the solution of geological problems, we are entirely indebted to Edward Forbes.
It is impossible to estimate too highly the value of the 'Theory of Bathymetrical Distribution' as a contribution to scientific natural history; and it is greatly to be regretted that the details of the Ægean researches, from which the theory was constructed, have never been published. A sum of money was granted by Government for the purpose, but the pressure of new avocations and other practical difficulties interfered. Nevertheless, Mr. Forbes always looked forward to the working up and publication of these his early and favourite investigations; and doubtless, the hoped-for leisure to carry out his pains was one of the many attractions which the Chair of Natural History in Edinburgh offered. But these projects were destined to have no fulfilment; and Forbes's views have but an incomplete representation in the 'Reports of the British Association' and the 'Memoirs of the Geological Survey of Great Britain.'
Edward Forbes's studies at the University were on the widest scale; and like the father of Natural History, he attacked with equal ardour Mineralogy, Botany, and Zoology. Good authorities affirm that his knowledge of mineralogy was of no small extent; as a
